Electrocarboxylation of CCI4 in MeCN during electrolysis with the sacrificial Zn anode
The regularities of galvanostatic electrocarboxylation of CCl4 in Alk4NBr/MeCN in an undivided cell with sacrificial Zn anode were studied. The major product of the electrolysis is zinc trichloroacetate, which is formed as a result of the reaction of the cathode-generated CCl3- anion with CO2. The further trichloroacetate reduction is prevented by cathode passivation. Therefore, small amounts of zinc dichloro- and monochloroacetates are formed due to the chemical reduction of zinc trichloroacetate with Zn0 rather than the cathodic reduction. Zero-valence zinc is formed in minor amounts when Zn2+ ions are discharged at the cathode surface because of the low solubility of ZnBr2 in MeCN. The treatment of (Cl3CCOO)2Zn with H2SO4 in MeOH gives Cl3CCO2Me in 11% yield based on the starting CCl4.
Key wordselectrochemical carboxylation sacrificial zinc anode tetrachloromethane carbon dioxide trichloroacetic acid
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